Interleukin-4 (IL-4), previously known as B cell stimulating factor, or BSF-1, was originally characterized by its ability to stimulate the proliferation of B cells in response to low concentrations of antibodies directed to surface immunoglobulin. IL-4 has been shown to possess a far broader spectrum of biological activities, including growth co-stimulation of T cells, mast cells, granulocytes, megakaryocytes, and erythrocytes. In addition, IL-4 stimulates the proliferation of several IL-2- and IL-3-dependent cell lines, induces the expression of class II major histocompatibility complex molecules on resting B cells, and enhances the secretion of IgE and IgG1 isotypes by stimulated B cells. IL-4 is associated with a TH2-type immune response, being one of the cytokines secreted by TH2 cells.
Murine and human IL-4 have been identified and characterized, including cloning of IL-4 cDNAs and determination of the nucleotide and encoded amino acid sequences. (See Yokota et al., Proc. Natl. Acad. Sci. USA 83:5894, 1986; Noma et al., Nature 319:640, 1986; Grabstein et al., J. Exp. Med. 163:1405, 1986; and U.S. Pat. No. 5,017,691.)
IL-4 binds to particular cell surface receptors, which results in transduction of a biological signal to cells such as various immune effector cells. IL-4 receptors are described, and DNA and amino acid sequence information presented, in Mosley et al., Cell 59:335-348, Oct. 20, 1989 (murine IL-4R); Idzerda et al., J. Exp. Med. 171:861-873, March 1990 (human IL-4R); and U.S. Pat. No. 5,599,905. The IL-4 receptor described in these publications is sometimes referred to as IL-4Rα.
Other proteins have been reported to be associated with IL-4Rα on some cell types, and to be components of multi-subunit IL-4 receptor complexes. One such subunit is IL-2Rγ, also known as IL-2Rγc. (See the discussion of IL-4R complexes in Sato et al., Current Opinion in Cell Biology, 6:174-179, 1994.) IL-4Rα has been reported to be a component of certain multi-subunit IL-13 receptor complexes (Zurawski et al., J. Biol. Chem. 270 (23), 13869, 1995; de Vries, J. Allergy Clin. Immunol. 102(2):165, August 1998; and Callard et al. Immunology Today, 17(3):108, March 1996).
IL-4 has been implicated in a number of disorders, examples of which are allergy and asthma. Studies of biological properties of IL-4 continue, in an effort to identify additional activities associated with this pleiotrophic cytokine, and to elucidate the role IL-4 may play in various biological processes and diseases.